The present invention relates in general to exposure control systems, and in particular, to a method and apparatus for providing exposure control based on color balance information.
Typical exposure control systems employ a photodetector to measure the illumination intensity of the scene to be photographed. Significant exposure errors may occur, however, if the photodetector is arranged to measure average illumination of the scene, as the average illumination may differ significantly from a subject area of the scene. For example, exposure error will frequently occur when a person is photographed against a bright sky or indoors against a window.
Exposure control systems have been devised that employ multiple photodetectors to monitor various zones of the scene in order to provide proper exposure of the subject area. The illumination contrast between zones is then used to determine proper exposure control. Exposure control based on contrast analysis, however, has not been found to be entirely satisfactory. Complex algorithms must be employed to determine whether various illumination contrast conditions between zones is indicative of a daylight scene, indoor fluorescent lighting, tungsten lighting, etc., which adds to the complexity and expense of the exposure control system.